Synergistic Effect of NiMoO₄ Nanorods with Polyaniline for Efficient Electrochemical Water Splitting

Electrochemical water splitting has emerged as a promising solution for sustainable hydrogen production, but the development of efficient, durable, and cost-effective bifunctional electrocatalysts remains a critical challenge. In this work, we report the novel fabrication of composite materials consisting of nickel molybdate (NiMoO₄) coated with polyaniline (PANI). NiMoO₄ nanorods were initially synthesized on nickel foam (NF) using a hydrothermal technique and subsequently coated with PANI via UV-assisted polymerization. The resulting NiMoO₄@PANI nanostructures demonstrate increased active sites for improved efficiency in electron transfer and catalytic activity. This combination enhanced hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performance, achieving reduced overpotential values of 88 and 167 mV for HER and OER at 10 mA cm^-2, respectively. Comprehensive electrochemical evaluations, including Tafel slope, electrochemical impedance spectroscopy (EIS), and electrochemical double-layer capacitance (C_dl) measurements, validate the enhancements in kinetics and charge transfer facilitated by the PANI coating. Density functional theory (DFT) calculations offer further insights into the improved catalytic efficiency, showing reduced barrier for water splitting (ΔG_b = 0.45 eV), nearly negligible hydrogen adsorption energy (ΔG_*H = 0.08 eV), appropriate adsorption energy of oxygen evolution (ΔG_*OOH - ΔG_*OH = 2.58 eV), and high density of states close to the Fermi level. The NiMoO₄@PANI nanostructures exhibit excellent stability for 310 h without interruption, suggesting the potential for sustainable hydrogen production.